I do hope you're joking micro as aside from reps being a bit sad, it also funds the worst of the criminal world; human trafficking, drug trade, terrorism, etc.
I am not joking about MrFlo though, anyone that has inate topstitching abilities on a domestic sewing machine is surely a witch that must be burned. (Sorry, MrFlo, I'm sure you're lovely).
Yes, I've been to the Montmartre fabric markets. Eh, they're not this mystical bazar as that (talented) writer makes them out to be. It's mostly end of rolls and furniture fabrics. I got some gorgeous linen/silk 50/50 gauze mix there that's waiting for inspiration to strike, I think I paid €15 for a 3 meter piece but it's actually a bit more meters than that. It's the place to go for cheap fabrics (I'm still cursing myself for not buying some off white wool end of roll coupon but it was heavy and bulky and would take up half my suitcase, I should have suffered the inconvenience or more sensibly, posted it home) and it's also kind of nice as it's very Paris of old. I recently reread Le Bonheur des Dames which very much revolves around the drapers trade and its impending extinction so if you want to relive the scenery of that book it's nice to go for that. I generally find the Montmartre area an annoying tourist hellhole but it definitely has its charm.
I could probably draw up a separate address book for Paris fabric and habidashery places but tbh nothing really stands out as a must visit. There's some beautiful shops with €€€€ haute couture fabrics but it's all a bit old fashioned. Then there's a lot of places like Montmartre that trade on being as cheap as possible and it's a real task to unearth a gem.
I think you're more on track with the ethnic boho look Red, I really like the Zara skirt, unfortunately the cheap river island looks a bit sad next to it. I think Ibiza is a bit confusing as you have the disco thumping club part of it and then more hidden are the disco thumping crowd of yesteryear which is a lot of old money hippies that either have a lot of it or very very little that meet up in the oddest places and out party the young disco thumping crowd. Brands worth looking at are a bit of old Isabel Marant, Mes Demoiselles, Ba&sh and the Greek beach/resort brands. I'm sure some Gaucho style things you might already have in your wardrobe would work too.